Indoline squaraine dye-based organic photodetectors to boost NIR sensitivity for titanyl phthalocyanine

In this work, a bulk heterojunction (BHJ) strategy was employed by doping squaraine (SQ2) into Y-type titanyl phthalocyanine (Y-TiOPc), aiming to optimize the device performance by adjusting the doping ratio of SQ2. The results revealed that the photodetector based on [email protected] %SQ2 exhibited excellent optoelectronic performance across a broad spectral range from 365 nm to 940 nm. Under a light intensity of 0.01 mW cm⁻², the device achieved a maximum photoresponsivity (R) of 109,634 mA W⁻¹ at 850 nm, with a corresponding external quantum efficiency (EQE) of 16,004 %. Compared to the Y-TiOPc-based photodetector, the [email protected] %SQ2-based device demonstrated significantly enhanced R and EQE values in the near-infrared (NIR) region, with increases by factors of 7.08 (700 nm), 6.28 (765 nm), 4.92 (850 nm), and 3.47 (940 nm), respectively. Moreover, the device showed a rapid, stable, and reproducible photoresponse. The performance enhancements are mainly attributed to the co-sensitization synergistic enhancement effect between Y-TiOPc and SQ2, as well as the improvement in carrier generation, separation, and transportation brought by the BHJ structure. This study demonstrates that the BHJ approach based on TiOPc and squaraine dye offers an effective strategy for improving photodetector performance by introducing squaraine doping to enhance NIR detection capabilities.